One of the conventional processes for coating forged parts, cast parts or the like of motorcars with paint is illustrated in FIG. 17 of Japanese Published Unexamined Patent Application No. 61-220758. According to the process illustrated therein, a number of hangers each hanging a material to be coated with paint are suspended from a trolley conveyor, and spray guns provided on both sides of the conveyor spray a paint and other necessary liquids to the material while the material is being conveyed by the conveyor. Another conventional process is illustrated in FIG. 18 of the above-mentioned Japanese Application. According to the process illustrated therein, a number of hangers each hanging a material to be coated are also suspended from a trolley conveyor, but the material is dipped in a paint and other necessary liquids filled in storages while being conveyed by the conveyor.
However, either of the above-mentioned conventional processes is not free from the defect that the material may not be coated at its entire surface or may not be covered with a coating of a uniform thickness. Also, since only one material to be coated can be hung from each hanger, only a relatively small number of materials can be coated by one process. Moreover, since the material to be coated is hung from the hanger of a relatively small size, only materials with relatively limited weights can be coated. Furthermore, for either of the above-mentioned conventional processes, it may may be necessary to use a device specially designed for holding the material to the hanger or to work out some other way of holding the material to the hanger. Also, since only one material can be hung from one hanger, either conventional process takes much time and trouble and, thus, has the defect that a great number of materials cannot be coated in a relatively short period of time.
The applicant has Japanese Pat. No. 1,339,372 and Japanese Utility Model Registration No. 1,650,688 which each disclose an electrodeposition-coating system where materials are electrodeposition coated and baked. Such a system may be effectively used to produce a coating of a uniform thickness on the entire surface of the material. The applicant also has Japanese Published Unexamined Patent Application No. 62-54097 which discloses a system similar to, but smaller than, those of the foregoing Japanese Patents. The system according to any one of these three prior arts comprises a number of hangers suspended from a conveyor for hanging a material to be electrodeposition coated, a plurality of tanks arranged in a required order and containing liquids required for electrodeposition coating the materials, and a furnace for baking the materials coated. In such a system, the materials hung from the hangers are immersed in the liquids in the tanks while being conveyed by the conveyor which is intermittently operated. However, the coating process by such a system is not free from the same defects as those of the foregoing two conventional coating processes. That is, since only one material is hung from each hanger, only a relatively small number of materials can be coated by one process. Also, since the material to be coated is hung from the hanger of a relatively small size, only materials with relatively limited weights can be coated. Moreoyer, it is necessary to use a device specially designed for holding the material to the hanger or to work out some other way of holding the material to the hanger. Also, since only one material can be hung from one hanger, such a process also takes much time and trouble and, thus, has the defect that a great number of materials cannot be coated in a relatively short period of time.